In his latest post Coen Jacons suggests that updating PHP is everyone's responsibility - that keeping the PHP installation on your systems up to date is important for everyone, not just the system administrators.

The number one remark I heard when I launched WPupdatePHP, is that users shouldn’t be bothered with this. In an ideal world, this is true, but in reality this isn’t going to stand for long. [...] I know the WordPress core team is working really hard to get webhosting companies to update their PHP versions and I agree up to a certain level that this is the best way. It’s not the only way though. [...] This will help lower the percentage of PHP 5.2 and 5.3 users out there. There still will be people on older PHP versions who are caught out and without them knowing what is going on, nothing will change for them.

He talks about the efforts the WordPress core team is doing to try to convince hosting providers to update, but points out that while WordPress aims to run on those old versions, staying on them is a mistake. He also mentions that an effort like this is a constant thing, always changing as the PHP versions released change. He ends the post with a "call to arms" for users out there, encouraging them to get talking to their hosting provider and get those PHP versions updated.

Don’t understand me wrong, I like what WordPress is doing to get these requirements bumped, but I think it’s not enough. I disagree on the fact that users shouldn’t be involved in this. It’s easy enough for users to request their hosting platform to be upgraded. If their request isn’t heard, they should find a better webhosting company. [...] It’s been long enough, I choose to act now.